Synthetic lubricants comprising dehydrocondensation products of polyesters



United States Patent 3,206,405 SYNTHETIC LUBRICANTS COMPRISING DE- I-IYDROCONDENSATION PRODUCTS 0F POLYESTERS Herbert L. Hepplewhite and Edward A. Oberright, Woodbury, and Robert H. Williams, Pennington, N.J., assignors to Socony Mobil Oil Company, Inc., a corporation of New York No Drawing. Filed Jan. 2, 1962, Ser. No. 163,908 14 Claims. (Cl. 252-56) This invention relates to the art of lubrication. More particularly, it is concerned with synthetic type lubricating oils comprising dehydrocondensation products of certain poyesters.

As is well known, mineral oils, which for many years had provided satisfactory lubrication for piston-engined aircraft, have proved to be inadequate for jet engines, due to the extreme ranges of temperatures to which the oil is subjected in jet aircraft. This need has been met by the development of synthetic-type lubricating oils, particularly the esters of dibasic acids. The latest types of turbo-jet and turbo-prop engines, however, have forced bearing and oil temperatures higher, i.e., up to 550600 F. In order to provide adequate lubrication for these newer engines, increased viscosity of the lubricating oil at these higher operating temperatures is required. At the same time, the viscosity-temperature characteristics of the oil must be such as to permit starting the engine at temperatures below at least about 30 F. Thus, the pour point of the oil must be below 30 F. or lower.

In accordance with the present invention, it has been found that conventional polyester lubricating oils when reacted with certain organic peroxides form dehydrocondensation products having high temperature viscosities which are substantially higher than those of the polyesters themselves. At the same time the low temperature viscosity levels and pour points of the products can be maintained within reasonable limits. Thus, it has also been found that the viscosities of the products can be controlled by the amount of peroxide employed in the dehydrocondensation reaction whereby the products are suitable either as lubricating oils, per se, or (in the case of highly viscous products) as blending agents for conventional ester-type oils to improve the viscosity-temperature characteristics thereof. Also, the products of the invention exhibit good shear-resistance as opposed to conventional polymeric oil addends. It is, therefore, the primary object of this invention to provide a novel class of lubricating oils comprising dehydrocondensation products of polyesters.

It is also an object to provide novel lubricating oil compositions comprising blends of conventional ester oils and dehydrocondensed polyesters.

Other objects and advantages of the invention will appear from the following detailed description thereof.

The polyesters which may be dehydrocondensed in accordance with the invention may be any polyester having an abstractable hydrogen atom. Thus, di-, triand tetraesters of di-, triand tetra-carboxylic acids and di-tri-, tetraand polyesters of glycols, triols and polyhydric alcohols may be employed. Non-limiting examples of suitable esters are the following:

Di-butyl phthalate Di-octyl adipate Di-Z-ethylhexyl sebacate Di-2-ethy1hexyl azelate Trimethylol propane trioctanoate Trimethylol propane tridecanoate Trimethylol butane hexanoate Pentaerythrityl tetraoctanoate Pentaerythrityl tetradodecanoate The organic peroxides utilizable in the invention may be any organic peroxide or hydroperoxide which breaks down on heating to give free radicals. However, tertiary alkyl peroxides containing from 8 to about 20 carbon atoms, such as di-t-butyl peroxide, di-t-amyl peroxide, tamyl, t-butyl peroxide and di-t-octyl peroxide, are particularly suitable.

The dehydrocondensation reaction is carried out by intermixing from about 5 to about 50 weight percent of the peroxide with the ester and heating the mixture for a period of from about 1 to about 10 hours at a temperature of from about 100 C. to about 200 C. Free alcohol formed in the reaction is then removed by distillation. The reaction can be carried out in one step utilizing relatively large amounts of peroxide, i.e., 15-20% or more, or it can be conducted in stages using relatively small amounts, such as about 5%, and repeating the reaction with this amount several times until a product having the desired viscosity is obtained. Thelatter procedure is useful in determining the amount of peroxide which will provide a product having a certain viscosity from a particular polyester, while the former procedure is generally the one used after such a determination has been made.

A full understanding of the invention will be had by reference to the following illustrative examples.

EXAMPLE 1 Dehydrocondensation of di-Z-ethylhexyl sebacate A mixture of 500 grams of di-Z-ethylhexyl sebacate and 25 grams of di-t-butyl peroxide were reacted under reflux at 135-145" C. for 5 hours. Tertiary butyl alcohol, formed during the reaction, was removed by distillation. A IOU-gram sample was then removed from the reaction mixture. The reaction mixture was then subjected to reaction with four additional portions of peroxide under the same conditions as in the original reaction, the portion of peroxide added in each instance amounting to ap proximately 5% of the remaining reaction mixture. Table I shows the physical properties of the products obtained in each of these reactions, numbered 1-5 in the table.

A separate reaction was also conducted under the conditions of the first of the preceding series of reactions, except that 18 weight percent of di-t-butyl peroxide was reacted all at once with the di-2-ethylhexyl sebacate. The properties of the product of this reaction (Reaction No. 6) are also given in Table I.

It will be seen from Table I that the viscosity of the dehydrocondensation product increases in proportion to the amount of peroxide employed in the reaction. However, the pour point of the products is not increased over that of the original ester.

TABLE I.PROPERTIES OF DEHYDROOONDENSED DI-Z-ETHYLHEXYL SEBACATE Unreacted Product of Product of Product of Product of Product of Product of polyester Reaction Reaction Reaction Reaction Reaction Reaction No.1 No.2 No.3 No.4 No.5 No.6

KV at 400 F., cs 1.08 1. 24 1. 48 1. 77 2.07 2. 23 2.00 KV at 210 F., cs 3. 31 4.12 5. 22 6. 75 8. 81 9. 65 8. 32 KV at 100 F., cs 12. 57 17. 30 24. 43 34. 88 50.17 56. 81 45. 78 KV at -40 F., cs. 1, 426 2, 625 4, 969 9, 364 17, 740 22, 340 ,910 ASTM slope .71 p 0.69 -0. 66 0. 64 0. 61 0. 61 -0. 62 Pe'rcentrecovery per tre 99. 3 99. 4 99. 4 99. 1 98. 2 97. 8 Flash point, 000, F--. 465 I 450 455 460 450: 440 API gravity 23.3 21.8 21. 6 20. 9 19.7 v 20.9 20.4 Neutralization N0. 0.1-7 0.14 0.44 0. 59 O. 66 0.68 i 0.60 Pour point, F '65 65 -65 '65' 65 65. -65

EXAMPLE 2 TABLE III.PROPERTIES O'F DEHYDROOONDENSATE OF Dehydrocondensatio'n of 'trimethylo'l ipropane trioctanoate A mixture of 503 grams of trimethylol propane trioctanoate and 25 grams o fdi-t-per'oxide were reacted under reflux at 140-150 "C. for 6 hours. Tertiary butyl alcohol, formed during the reaction, was removed by distillation. A IOO-gram "sample was then removed from the reaction mixture. subjected to reaction with three additional portions of peroxide under the same conditions as the original reaction. A sample of the reaction mixture (product) was taken after each reaction. The portionof peroxide added in each instance amounted to approximately "%,fby Weight, of the remaining reaction mixture. The physical properties of the products of these four reactions are given "in Table II.

Here again, it "is seen that the "viscosities of the .products are greater than those of the original'ester and that the viscositie-s increase in proportion to 'the amount of peroxide used. At the same time, however, the rpour pointof the products remains unchanged,

The reaction mixture was then TRIMETHYLO'L PROPAN E TRIPELARGONATE Unreacted Dehydroconester 'densation product Flash point, F 525.0 530 EXAMPLE 4 Dehydrocondensation of Hercolube 600 A mixture 502 grams of Hercolube 600 (a mixed 0 c fa'tty acid ester of pentaerythritol) and 25 grams of di-t-butyl peroxide were reacted under reflux at 140 C. to 150 C.'for-'6#hours. Tertiary bu'ty l alcohol, formed during the reaction, was removed by distillation. A 100- gram sample was removed from the reaction mixture. The reaction mixture Was subjected to 3 further reactions PROPANE "IRIOCTANOATE Unre'acted Product of Product of Product of Product of polyester Reaction Reaction Reaction Reaction No. 1 No 2 No. 3 No. 4

1. 12 1137 1. 66 2.13 2.81 .4. 21 i 533 6. 98 10.00 14. 51 19:60. 28. 42 41. 62 65. 42 113.8 "4,067 8,534; 18,444 48,928 APIgra'vity 16:8 15:9 1 15. 3 4.1 13. 7 Neutralization No. 0. 10 0.76 1. 1 1. 2 1: Pour point, '30 =30 '80 30 30 Flash point, F 470 480 485 495 p 500 EXAMPLE 3 as in Examples 1 and 2, 1.e., by adding fresh portions of eroxide amounting in each instance to about "5% 'by "Deb drocondensatzon o trzmet l0 1 a p y f hy 1p r OF M Weight, of the reaction mixture after Withdrawal of -trz pelarg0nate 55 I In this example the trimethylol propane tripela'rgonate was reacted for '6 hours with 15%, by Weight, of -di-t- 'butyl peroxide at -1-3"5l50 C. The -t-'bu't-y1 alcohol formed in the reaction was removed by distillation. The

:prope'rties'of theoriginal ester and thedelrydrocondensate productare shown'in Table =I-II.

TABLE IV.DEHY*DROOONDENSATION OF HERCODUBE 600 {MIXED (lg-C1 ACID ESTER OF PENTA-ERY-IH-RITOL Unre'acted Product of Productof Product-of Product of polyester Reaction Reaction Reaction Reaction No.1 No.2 No.3 No.4

at 400 F 1.27 1. 71 2. 32 3.48 6. 04 KV at 210 F 4. 7. 45 v 11. 46 20. 21 41. 63 KV at F 26. 42 46. 80 86.- 82 185. 8 478. 2 EV at 4 0 F".-. 8, 28, 787 100x10 200x10 .APIgravity 9.8 9. 0' '7. 8 6. 8 6. 4 Neutralization No. 0.17 0.22 0. 40 i 0.48 0. 87 Four point, ]3 30 -30 -30 30 --10 Flash point, F--. 495 515 500 '515 Molecular'weight- 555 660 780 1, 200

5 EXAMPLE 5 Preparation of blending agent from Hercolube 600 Hercolube 600 Was refluxed With 25 weight percent of di-t-butyl peroxide at 140-150 C. for several hours. In the course of stripping the product, a gel was formed. Liquid product was extracted with toluene, in which the gel is insoluble. This material (extract) was used as a blending stock in di-Z-ethylhexyl sebacate, trimethylol propane trioctanote and Hercolube 600. Properties of the blends, as well as Sonic Oscillator shear data, are given in Table'V.

It will be seen that the dehydrocondensed ester is highly advantageous as a blending stock for the estertype oils, since it substantially increases both the viscosity and viscosity index of the base ester oil. It is seen further than the 10% treated-ester blend does not significantly detract from the shear stability of the (di-2- ethylhexyl sebacate) oil.

Results similar to those shown in Table V are attained with blends of the products in conventional ester oils other than di-Z-ethylhexyl sebacate. As is well known, these ester oils are derived from either (a) monohydric aliphatic alcohols, such as butyl, iso-butyl, octyl, decyl, dodecyl and tetradecyl alcohol, and aliphatic dicarboxylic acids, such as adipic, pimelic, suheric, azelaic and sebacic acid, or (b) polyhydric alcohols, such as ethylene glycol, trimethylol propane, trimethylol butane, pentaaerythritol, etc., and monocarboxylic acids, such as acetic, valeric, decanoic, myristic, stearic, etc.

TABLE V.-PROPERTIES OF HERCOLUBE 600 DEHYDROCONDENSATE 1 BLENDS Dehydro- Base fluid condensate, KV at KV at KV at V1 wgt. -40 F. 100 F. 21 F. percent Di-2cthylhcxyl scbacate 1,425 12. 55 3. 31 154 5 2, 155 18. 02 4. 58 185 3, 225 25. 46 6. 23 173 5, 079 36. 23 8. 55 166 Trimethylol propane trioctanoate.. 0 4, 067 19. 4. 21 139 5 6, 435 28.09 5. 74 151 10 10, 140 40. 18 7. 48 152 15 15,042 57. 75 11. 01 150 Hcrcolube 600 0 8, 160 26. 42 4. 95 129 5 14, 180 39. 06 7. 21 143 10 23, 111 56. 45 9. 86 143 15 39, 596 83. 2 13. 98 143 Sonic Oscillator Shear Test: 2

Sample=l0 wgt. percent of Hercolube 600 dehydrocondensate in di-2-ethylhexyl sebacate. KV at 210 F. Original=6.23

Final=5.92 Percent Changc=5 (1) Hercolube 600 dehydrocondensate: KV at 210 F.=748.6.

(2) ASTM Proposed Test Method, Preprint 35-S, 1961, Appendix XII, page 61.

EXAMPLE 6 Dehydrocondensation 0f fluoroallq l camphorate TABLE VI.PROPERTIES OF FLUOROALKYL CAMPHORATE DEHYDROCONDENSATION PRODUCT Unreacted ester Dehydroeondensation product at 115. 5 8, 114 KV at 210 F 8.22 97. 96 Flash point, F 460 525 As shown in Tables I-IV, the neutralization number (N.N.) of the dehydrocondensation product in some instances is slightly higher than that of the starting polyester. However, this increase in N.N. can be eliminated by simple percolation over a suitable adsorbent, such as alumina or florisil.

Table VII shows the results obtained by the percolation treatment of a dehydrocondensed trimethylol propane tripelargonate ester. It will be seen that the product which was not subjected to percolation had an N.N. of 0.28, but that the N.N. of the percolated product with or without thermal treatment (columns 2 and 3) was lowered to substantially that of the original ester.

It has been found also that reaction of the starting ester with over about 10%, by weight, of peroxide provides a product of somewhat lower thermal stability than that of the starting ester. However, this may be overcome by subjecting the product to a simple thermal treatment. This involves simply heating the product to a temperature of, say, 400600 F. in a nitrogen atmosphere. Table VIII shows the effect of the thermal treatment on the thermal stability of a dehydrocondensed trimethylol alkane tripelargonate. It will be seen from the table that percolation alone has only a minor effect on the thermal stability of the product, while heat-treating results in a large improvement in thermal stability. Percolation used after heat-treating removes acidic decomposition products and improves the color of the product.

TABLE VII.EFFECT OF THERMAL TREATMENT AND/OR 1 Heated at 536 F. for 24 hours under nitrogen and percolated over clay and alumina.

TABLE VIII.THERMAL STABILITY OF TREATED AND UNTREATED DEHYDROOONDENSED TRIMETHYLOL PROPANE TRIPELARGONATE 15% di-t-butyl peroxide reaction product Thermally No treatment percolated treated and percolated 2 Weight loss, percent change. 0.3 0.0 0. 4 EV at F., percen change.... --29. 7 -23. 2 +3. 3 EV at 210 ercent change 24. 7 22. 0 +0. 8 Neutralization Number.... 2. 5 1. 6 0. 0

1 Test Method: Sample heated to 536 F. in nitrogen atmosphere for 24 l i e ated at 536 F. for 24 hours under nitrogen and percolated over clay and alumina.

It will be seen that the invention (1) provides polyester dehydrocondensation products having viscosities and low temperature characteristics which make them desirable lubricating oils for high temperature application, such as jet engine lubricants and (2) that these products are highly advantageous blending agents for conventional ester lubricating oils. It will be understood that the amount of the dehydrocondensatlon product added to an ester base oil can vary over a wide range, depending upon the viscosity of the particular product used and the viscosity desired in the finished blend. Thus, the products, being lubricating oils of themselves, may comprise either a major or a minor proportion of the finished oil blends. From the standpoint of increasing the viscosity and/or viscosity index of the ester-base oil, however, the amount of dehydrocondensation product employed will generally be no greater than about 40 weight percent and may be as little as 1 weight percent, based on the total composition.

The lubricating oil compositions of the invention may contain additives normally added to lubricating oil for the purpose of improving the various characteristics thereof, such as antioxidants, detergents, extreme pressure agents, anti-wear agents, metal deactivators, etc.

Although the invention has been illustrated herein by means of specific examples and embodiments thereof, it is not intended that the scope of the invention be limited in any way thereby except as defined in the following claims.

We claim:

1. A lubricating oil comprising a dehydrocondensation product prepared by reacting (a) a polyester derived from a carboxylic acid, selected from the group consisting of monoand polycarboxylic acids, said acids containing from about 2 to about 20 carbon atoms exclusive of carboxyl carbons, and an alcohol, selected from the group consisti-ngof monoand polyhydroxy alcohols, said alcohol containing from about 2 to about 20 carbon atoms with (b) from about 5% to about 50%, by weight, based on the polyester, of a di-tertiary alkyl peroxide containing from about 8 to about 20 carbon atoms, at a temperature of from about 100 C. to about 200 C. to form a dehydrocondensation product of said polyester and removing free alcohol formed in the reaction from the dehydrocondensation product.

2. A lubricating oil comprising a dehydrocondensation product prepared by reacting di-Z-ethylhexyl sebacate with from about 5% to about 50%, by weight, based on the weight of the di-2-ethylhexy1 sebacate, of di-tertiarybutyl peroxide, at a temperature of from about 100 C. to about 200 C., to fornra dehydrocondensation product of di-Z-ethylhexyl sebacate and removing free -di-tertiary- 'butyl alcohol formed in the reaction from the dehydrocondensation product.

3. A lubricating oil comprising a dehydrocondensation product prepared by reacting trimethylol propane trioctanoa'te with from about 5% to about 50%, by weight, based on the weight of the trimethylol propane trioctanoate, of 'di-tertiary-butyl peroxide, at a temperature of from about 100 C. toabout 200 C., to form a dehydrocondensation product of trimethylol propane trioctanoate and removing free di-tertiary-butyl alcohol formed in the reaction from the dehydrocondensation product.

4. A lubricating oil comprising .a dehydrocondensation product prepared by reacting trimethylol propane tripelargonate with from about 5% to about 50%, by weight, based on the wei ht of the trimethylol propane 'tripelargonate, of di-tertiary-butyl peroxide, at a temperature of from about 100 C. to about 200 C., to form a de hydrocondensation product of trimethylol propane tripelargonate and removing free di-tertiary-butyl alcohol formed in the reaction from the dehydrocondensation product.

5. A lubricating oil comprising a dehydrocondensation product prepared by reacting a mixed C C carboxylic acid ester of pentaerythritol with from about 5% to about 50%, by weight, based on the weight of said ester, of di-tertiary-butyl peroxide, at temperature of from about 100 C. to about 200 C., to form a dehydrocondensation product of the mixed C C carboxylic acid ester of pentaerythritol and removing free-di-tertiary-butyl alcohol formed in the reaction from the dehydrocondensation product.

6. A lubricating oil composition comprising a blend of a conventional ester oil and a dehydrocondensation product prepared by reacting (a) a polyester derived from a carboxylic acid, selected from the group consisting of monoand polycarboxylic acids, said acids containing from about 2 to about 20 carbon atoms exclusive of carbox l carbons, and an alcohol, selected from the group consisting of monoand polyhydroxy alcohols, said alcohol containing from about 2 to about 20 carbon atoms with (b) from about 5% to about 50%, by weight, based on the polyester of .a di-tertiary .alkyl peroxide containing from about 8 to about 20 carbon atoms, at a temperature of from about C. to about 200 C. to form a dehydrocondensation product of said polyester and removing free alcohol formed in the reaction from the dehydrocondensation product.

7. A lubricating oil composition comprising a blend of a conventional ester oil and a dehydrocondensation product prepared by reacting di-2-ethylhexyl sebacate with from about 5% to about 50%, by weight, based on the Weight of the =di-2-ethylh'exyl sebacate, of di-tertiary- .butyi peroxide, at a temperature of from about 100 C. to about 200 C., to form a dehydrocondensation product of di-Z-ethylhexyl sebacate and removing free ditertiary-alcohol formed in the reaction from the dehydrocondensation product.

8. A lubricating oil composition comprising a blend of a conventional ester oil and a dehydrocondensation product preparted by reacting trimethylol propane trioctanoate with from about 5% to about 50%, by weight, based on the weight of the trimethylol propane trioctanoate, of ditertiary-butyl peroxide, at a temperature of from about 100 C. to about 200 C., to form a dehydrocondensation product of trimethylol propane trioctanoate and removing free di-tertiary-butyl alcohol formed in the reaction from the dehydrocondensation product.

9. A lubricating oil composition comprising a blend of a conventional ester oil and a dehydrocondensation product prepared by reacting trimethylol propane tripelargonate with from about 5% to about 50%, by Weight, based on the weight of the trimethylol propane tripelargonate, of di-tertiary-butyl peroxide, at a temperature of from about 100 C. to about 200 C., to form a dehydrocondensation product of trimethylol propane tripelargonate and removing free di-tertiary-butyl alcohol formed in the reaction from the dehydrocondensation product.

10. A lubricating oil composition comprising a blend of a conventional ester oil and a dehydrocondensation product prepared by reacting a mixed C -C carboxylic acid ester of pentaerythritol with from about 5% to about 50%, by weight, based on the weight of said ester, of di-tertiary-butyl peroxide, at a temperature of from about 100 C. to about 200 C., to form a dehydrocondensation product of the mixed C C carboxylic acid ester of pentaerythritol and removing free di-tertiary-butyl alcohol for-med in the reaction from the dehydrocondensation product.

11. A lubricating oil as defined in claim 1 which has been improved as to its thermal stability by heating to a temperature of from about 400 F. to about 600 F. in a nitrogen atmosphere.

12. The lubricating oil composition of claim 6, wherein the amount of dehydrocondensation product blended with the conventional ester oil is from about 1% to 40%, 'by weight, of total composition.

13. A lubricating .oil comprising a dehydrocondensation product prepared by reacting a polyester having an abstractable hydrogen atom with from about 5% to about 50%, by weight, based on the polyester, of a di-tertiary :alkyl peroxide containing from about 8 to about 20 carbon atoms, at a temperature of from about 100 C. to about 200 C. to form a dehydrocondensation product of said polyester and removing free alcohol formed in the reaction from the dehydrocondensation product.

14. A lubricating oil composition comprising a blend of a conventional ester oil and a dehydrocondensation product prepared by reacting a polyester having an abstractable hydrogen atom with from about 5% to about 50%, by Weight, based on the polyester of a di-tertiary 9 10 :alkyl peroxide containing from about 8 to about 20 2,808,418 10/57 Harrison 260404.8 carbon atoms, at a temperature of from about 100 C. 2,820,014 1/58 Hartley et a1. 25256 to about 200 C. to form a dehydrooondensation pnod-uct 2,839,571 6/ 58 Johnston et a1. 260485 of said polyester and removing free alcohol formed in 2,961,406 11/60 McNeil et a1. 252-56 the reaction from the dehydrocondensation product. 5 2,993,360 7/ 61 Critchley 252-57 FOREIGN PATENTS References Cited by the Examiner 591,543 8/47 Great Britain.

UNITED STATES PATENTS 2 429 219 10 47 Cowan 2 407 X 10 DANIEL WYMAN, 'y Exammer- 2,801,263 7/57 Hasek et a1, 260485 JULIUS GREENWALD, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Now 3,206,405 September 14, 1965 Herbert L., Hepplewhite et ale It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 21, for "di-t-perOXide read di-t-butyl peroxide column 6, TABLE VII, in the heading to columns v2, 3 and 4, for "15% di-t-butyl perTxide" read 15% di-t-butyl peroxide column 8, line 25, for "preparted" read m prepared Signed and sealed this 24th day of May 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER testing Officer Commissioner of Patents 

6. A LUBRICATING OIL COMPOSITION COMPRISING A BLEND OF A CONVENTIONAL ESTER OIL AND A DEHYDROCONDENSATION PRODUCT PREPARED BY REACTING (A) A POLYESTER DERIVED FROM A CARBOXYLIC ACID, SELECTED FROM THE GROUP CONSISTING OF MONO- AND POLYCARBOXYLIC ACIDS, SAID ACIDS CONTAINING FROM ABOUT 2 TO ABOUT 20 CARBON ATOMS EXCLUSIVE OF CARBOXYL CARBONS, AND AN ALCOHOL, SELECTED FROM THE GROUP CONSISTING OF MONO- AND POLYHYDROXY ALCOHOLS, SAID ALCOHOL CONTAINING FROM ABOUT 2 TO ABOUT 20 CARBON ATOMS WITH (B) FROM ABOUT 5% TO ABOUT 50%, BY WEIGHT, BASED ON THE POLYESTER OF A DI-TERTIARY ALKYL PEROXIDE CONTAINING FROM ABOUT 8 TO ABOUT 20 CARBON ATOMS, AT A TEMPERATURE OF FROM ABOUT 100*C. TO ABOUT 200*C. TO FORM A DEHYDROCONDENSATION PRODUCT OF SAID POLYESTER AND REMOVING FREE ALCOHOL FORMED IN THE REACTION FROM THE DEHYDROCONDENSATION PRODUCT. 